Experimental Investigation on the effect of air in pumping non-settling fluids

Authors

Nicola Zanini  - University of Ferrara, Italy
Alessio Suman - University of Ferrara, Italy
Michele Pinelli - University of Ferrara, Italy
Johann Friedrich Gülich - Independent Consultant, Villeneuve, Switzerland

Abstract

Non-Newtonian fluids are involved in many industrial processes, for example in food and Oil&Gas applications. Since their viscosity varies with the imposed stress and rheology, pumping this type of fluids can lead to a considerable variation in the pump head, and overall efficiency difficult-to-be-predicted. Previous experimental experiences reported that detrimental effects arise at low flow rates. Since most of the manufacturers test their pumps only with water, the selection of the appropriate pump to handle non-Newtonian fluids may result very challenging. As a consequence, oversized pumps are commonly installed. According to literature, this phenomenon could be ascribed to the free air trapped in the fluid. However, further investigations are needed to better understand the main causes of the variation in the pump head and efficiency as the first step to better predict the pump performance during operation with non-Newtonian fluids. In this work, an experimental investigation on a small centrifugal pump handling mixtures of water and kaolin was carried out. Different free air volume contents were also considered during tests. A critical analysis was conducted to relate the pump performance variation with the air. The experimental results were then compared with the ones predicted by several literature models.